Nowadays, in case of bonding a composite resin as a cavity filling material to dentin of tooth with a bonding agent or bonding a metal such as an inlay and a crown to dentin of tooth with an adhesive resin cement, after treating the surface of the dentin of tooth, usually such a method is employed to adhere a bonding agent or an adhesive resin cement to the dentin of tooth, and bond a composite resin through the bonding agent or bond a metal through the adhesive resin cement to the dentin of tooth. The surface treatment of dentin of tooth includes etching treatment and primer treatment. In etching treatment, a surface of dentin is made rugged due to decalcification by dissolving a smear layer and hydroxylapatite of the dentin, followed by penetrating of a bonding agent or an adhesive resin cement into the rugged surface and hardening thereof to enhance their mechanical holding strength and enable to adhere the dentin to the bonding agent or the adhesive resin cement. Primer treatment modifies the dentin of tooth to a suitable state for adhering the bonding agent or the adhesive resin cement.
Such a method for the surface treatment of dentin includes, for instance, a method of etching treatment of dentin with ethylenediamine tetraacetic acid (EDTA) followed by primer treatment with a mixed aqueous solution of glutaraldehyde and 2-hydroxyethylmethacrylate (HEMA) (Munksgaard, E. C., et al., J. Dent. Res., 63(8), 1087-1089, 1984), a method of etching treatment of dentin by deashing with an aqueous solution of orthophosphoric acid, followed by primer treatment for a collagen layer of the dentin with an aqueous solution of HEMA after air drying (Sugisaki, et al., Jpn. J. Conserv. Dent., 34(1), 228-265, 1991; Meerbeek, B. V., et al., J. Dent. Res. 72(2), 495-501, 1993; Pashley, D. H., et al., Quintessence Int. 24(9), 618-631, 1993), and the like.
In order to simplify the surface treatment of dentin, studies have been prevalent on a self-etching primer agent with which both of etching treatment and primer-treatment are performed at the same time. With regard to a self-etching primer agent, for instance, use of N-acryloylaspartic acid (N-AAsp), a derivative of aspartic acid as one of dicarboxylic acids, is proposed as a self-etching primer agent (Ito, et al., Dental Material and Apparatus, 15(4), 341-347, 1996; Ito et al., Dental Material and Apparatus, 16(2), 155-159, 1997; Ito, et al., Dental Material and Apparatus, 16(1), 38-43, 1997). The N-AAsp is considered to decalcify the dentin as an acidic monomer and at the same time act on both of an inorganic material and an organic material in dentin as a functional monomer.
Lately, studies have been prevalent on a self-etching primer agent applicable to both of dentin and enamel (Watanabe, Dental Material and Apparatus, 11(6), 955-973, 1992; Fukushima, et al., Dental Material and Apparatus, 11(4), 679-684, 1992). These self-etching primer agents comprise an acid or an acidic monomer capable of decalcification and a functional monomer to promote diffusion and penetration of a bonding agent. In addition, a mixed aqueous solution of N-methacryloylalanine and HEMA has been proposed as a self-etching primer agent for dentin and enamel (Takahashi, et al., Dental Material and Apparatus, 9(1), 65-73, 1990). With regard to an action mechanism of the agent, it is considered that N-methacryloylalanine decalcifies hydroxyapatite as an acid to make a collagen fiber being exposed, on which HEMA acts as a primer.
On the other hand, it has been reported that a strong adhesion of a composite resin to dentin can be obtained by treating the dentin etched by an aqueous solution of phosphoric acid with an N-methacryloyl-ω-amino acid such as N-methacryloylglycin, N-methacryloyl-4-aminobutyric acid and N-methacryloyl-6-aminocaproic acid as a primer agent (Nishiyama, et al., Dental Material and Apparatus, 13(1), 73-77, 1994; Nishiyama, et al., Dental Material and Apparatus, 17(2), 120-125, 1998). However, use of such an N-methacryloyl-ω-amino acid as a self-etching primer agent has not been so far known.